1. Field of the Invention
The invention relates to a lens. More particularly, the invention relates to a zoom lens.
2. Description of Related Art
Referring to FIG. 1, a zoom lens 100 disclosed in U.S. Pat. No. 5,552,937 includes a first lens group 110 and a second lens group 120. The first lens group 110 is composed of three lenses 112, 114, 116, and the second lens group 120 is composed of four lenses 122, 124, 126, 128. In the zoom lens 100, in order to eliminate image aberration and chromatic aberration, more than one aspheric lens is used in the first lens group 110 and the second lens group 120. That is, many aspheric lenses are used in the zoom lens 100 to achieve a wide angle.
Although the aspheric lens has a fine effect for rectifying image aberration, a strict tolerance requirement is brought forward in the mass production when too many aspheric lenses are used. If the tolerance is not controlled in the mass production, the overall yield is reduced. Moreover, since the aspheric lens has a high cost, the cost of the zoom lens 100 is increased if too many aspheric lenses are used in the zoom lens 100.
Referring to FIG. 2, a zoom lens 200 disclosed in U.S. Pat. No. 6,839,183 includes a first lens group 210, a second lens group 220, and a third lens group 230. The first lens group 210 is composed of three lenses 212, 214, 216, the second lens group 220 is composed of three lenses 222, 224, 226, and the third lens group 230 is composed of one lens 232. Moreover, the zoom lens 200 further includes an aperture stop 240 movably disposed between the first lens group 210 and the second lens group 220.
During the zoom lens 200 zooms in/zooms out, the aperture stop 240 moves together, thus the interlinking mechanism of the zoom lens 200 is quite complicated. Thereby, not only the volume of the zoom lens 200 is enlarged, but also the manufacturing cost of the zoom lens 200 is increased.